Removal of Cu(II) by MgAl-OH LDHs/birch leaves composites prepared by ball-milling hydrothermal method and mechanism insight

Abstract

Using Al(OH)3 and Mg(OH)2 as raw materials, MgAl layered double hydroxides (LDHs) modified from birch leaves were prepared by the ballmilling- hydrothermal method, denoted as LDHs/BL, and used for the treatment of wastewater containing Cu(II). The morphology, crystal shape, and specific surface area of the samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and BET-specific surface area analyzer. The results showed that the prepared LDHs/BL composites had good crystal shape, large specific surface area, and suitable pore structure. Langmuir and Freundlich adsorption isotherm models were used to analyze the adsorption. The results showed that the adsorption conforms to the Freundlich adsorption isotherm model. Under the same adsorption conditions, the adsorption capacity of the LDHs/BL complex was higher than that of LDH, the removal efficiency of the former was 92%, and that of the latter was 68%. The adsorption mechanism includes metal precipitation and isomorphic replacement. More importantly, this study provides a green method to prepare LDHs. LDHs/BL composites are expected to be used as a new kind of environmental adsorbent for wastewater treatment. This work provides a new idea for the utilization of agricultural and forestry wastes.